ISO 9001:2015 has no requirement for the existence of an organization chart. When the process approach was introduced in the ISO 9001:2000 version that requirement was deleted because in the limit the process approach and the organization chart represent two conflicting ways of managing an organization.
Having written that, once organizations use organization charts and mention them on their documentation it is usual for auditors to request it, during audits. Also, I believe that some auditors ask for it because they think it is an ISO 9001 requirement.
The following material will provide you more information about responsibilities and authorities: